A home base station is a base station used in a home, including the Home evolved Node B (HeNB) and the Home Node B (HNB). The HeNB is a home base station in the Long Term Evolution (LTE) system and the HNB is a home base station in the Universal Mobile Telecommunication System (UMTS). FIG. 1 shows the connection structure of the HNB in the existing UMTS. As shown in FIG. 1, the User Equipment (UE) is connected to the HNB through the Uu interface, the HNB is connected to the home base station gateway (HNB GW) through the Iuh interface, and the HNB GW is connected to the Serving General Packet Radio Service (GPRS) Support Node (SGSN) in the Core Network (CN) through the Iu interface.
The LTE technology is an evolved technology of the third generation (3G) mobile communication system, which is advantageous in that it may improve the cell capacity and reduce the system delay, etc.
FIG. 2 is a schematic diagram illustrating the construction of the existing LTE system. As shown in FIG. 2, the Evolved Universal Terrestrial Radio Access Network (E-UTRAN) of the LET system mainly includes the radio resource management entity, such as the macro base station (eNB) and the home base station (HeNB), etc., and may further include the home base station gateway (HeNB GW). When the HeNB GW is not included, the HeNB may be connected to the Mobile Management Entity (MME) of the core network directly; When the HeNB GW is included, the HeNB is connected to the MME through the HeNB GW. The MME is an important network entity of the core network, realizing the functions of radio access bearer establishing and mobile management, etc.
In order to provide the UE with more access services, there may be many kinds of HNB/HeNB, such as the open HNB/HeNB, the mixed HNB/HeNB and the Closed Subscriber Group (CSG) type HNB/HeNB. Each CSG has CSG identification witch identifies this CSG uniquely. The open HNB/HeNB has no specific limitation to the accessed UE, that is, any UE may access the open HNB/HeNB; the CSG HNB/HeNB only allows the access of the specific UEs (in order to facilitate description, the specific UE is simply referred to as a CSG UE in the following) which is served by the HNB/HeNB; the mixed HNB/HeNB may allow the access of the CSG UE which is served by the HNB/HeNB in order to provide this CSG UE with better quality access services, and at the same time may allow the access of non-CSG UEs.
In the UTMS system, the UE may implement relocation process when moving among HNBs; correspondingly, in the LTE system, the UE may implement handover process when moving among different HeNBs or between the HeNB and eNB. Essentially, both relocation process and handover process are the procedures which are implemented when the UE (in connection mode) moves among different base stations (such as eNB or Radio Network Control entity RNC) or cells. The difference between the two processes only lies in that the particular procedures have little difference when they are applied to different systems. The existing relocation process and handover process also have similar drawbacks, descriptions of which are given as follows.
Currently, when the UE implements relocation among various HNBs under one HNB GW, the relocation is implemented through the SGSN, which certainly will increase the burden of CN, so as to cause the degradation of the relocation performance. Therefore, a method of relocation for optimizing the UE according to prior art is proposed. Referring to FIG. 3, the method includes the following steps.
Step 301: the UE is connected to the CN through the source (S)-HNB and the HNB GW, the Circuit Switched domain (CS) and/or Packet Switched domain (PS) services between the UE and the CN are activated.
Step 302: the S-HNB decides to perform relocation for the UE in CS and/or PS services currently.
Step 303: the S-HNB determines whether the relocation is performed through the home base station application protocol (HNBAP) or the Radio Access Network Application Part (RANAP) signaling according to information of the HNB neighbor cell. If the S-HNB chooses to trigger the HNBAP relocation process, the HNB sends a HNBAP relocation request message to the HNB GW. The message contains global cell identifications for the source cell and destination cell, UE context and all requisite information all other destination HNBs requests the relocated UE to carry.
Step 304: alternatively, access control or member verification process may be performed to the UE. This step is not an emphasis of the present invention and hereby the detail technical description of which is omitted.
Step 305: the HNB GW transfers the HNBAP relocation request message to the destination (T)-HNB. The HNB GW adds the upstream transport layer parameters to the message. The relocation request message may implement implied UE registration process.
Step 306: the T-HNB sends a HNBAP relocation response message to the HNB GW.
Step 307: the HNB GW transfers the relocation response message to S-HNB.
Step 308: After the HNBAP relocation preparation, the S-HNB starts the RRC reconfiguration process, instructing the UE to move to the destination HNB.
Step 309: the UE sends RRC connection reconfiguration complete message to T-HNB.
Step 310: the S-HNB sends a HNBAP relocation commit message to the HNB GW.
Step 311: the HNB GW transfers the HNBAP relocation commit message to T-HNB.
Step 312: the T-HNB sends a HNBAP relocation complete message to the HNB GW. This message informs the HNB GW that the relocation is completed.
Step 313: the HNB GW sends a RANAP user adaptation (RUA) disconnect message to S-HNB.
Step 314: the HNB GW sends a HNBAP UE de-register message to S-HNB. the S-HNB releases reserved resource to the UE.
The transmission of user plane data between the HNB and the CN may be implemented through one tunnel or two tunnels. One tunnel means that the user plane data is transmitted from the HNB to the CN directly or from the CN to the HNB directly; two tunnels means that the user plane data is transmitted from the HNB to the HNB GW and then to CN, or from the CN to the HNB GW and then to the HNB.
In the LTE, the transmission of user plane data between the HeNB and the CN may be implemented through one tunnel or two tunnels. One tunnel means that the user plane data is transmitted from the HeNB to the S-GW/PDN GW directly or from the 5-GW/PDN GW to the HeNB directly; two tunnels means that the user plane data is transmitted from the HeNB to the HeNB GW and then to the S-GW/PDN GW, or from the S-GW/PDN GW to the HeNB GW and then to the HeNB.
As can be seen from the optimized relocation process shown in the above FIG. 3, the S-HNB determines whether the optimized relocation process (such as HNBAP relocation process) is started, that is the relocation process ending at the HNB GW, or the existing RANAP relocation process is started. The existing RANAP relocation process is described in detail in 3GPP TS23.060, the detailed technical description of which is omitted. If the user plane data is transmitted through one tunnel, when the UE moves from the S-HNB to T-HNB, there is a need for the CN to know the change of the downstream user plane, therefore, HNBAP relocation process may not be used; however, currently, the HNB is incapable of knowing whether the user plane data is transmitted through one tunnel or two tunnels, therefore, the existing relocation process tends to cause the failure of relocation, so as to reduce the relocation efficiency.
Similarly, in the LTE system, there are similar problems when the UE is performing handover between different HeNBs or between the HeNB and eNB. The handover mode may be the original S1 handover or the optimized handover (such as X2 handover). If it is the S1 handover, the S-HeNB sends S1 access protocol (AP) handover request message to the HeNB GW (in the case that there is the HeNB GW deployment); if it is X2 handover, the S-HeNB sends X2AP handover request message to T-HeNB or sends it to T-HeNB through the HeNB GW. If X2 handover also ends at the gateway, the HeNB also needs to know whether the user plane data is transmitted through one tunnel or two tunnels, and at the same time, needs to know whether the HeNB GW supports the X2 protocol. However, currently, the HeNB is unable to know whether the HeNB GW supports the X2 protocol. In addition, when the UE is performing handover from the HeNB to eNB, in the case of choosing to use the mode of performing X2 handover through the HeNB GW, some conditions are required to be satisfied in addition to the need for the HeNB GW to support X2 protocol, for example, there is a X2 interface between the HeNB GW and the destination eNB, and there is a S1 interface between the destination eNB and the source MME of UE. However, the existing HeNB does not know the information. Since the HeNB is unable to know the above information, the existing handover process tends to cases the failure of handover, which reduces the handover efficiency.
It can be seen from the above, in the existing relocation/handover process, since it is unable to determine whether the optimized relocation/handover mode may be used according to necessary information, the relocation/handover tends to be failed, which reduces the efficiency.